TOPIC SCHEDULE week
9
TOPIC SCHEDULE Today’s Lecture: Building materials: Concrete and Reinforced concrete A form of cement was used even in roman times, however, the development of building materials and engineering techniques - especially our knowledge on reinforced concrete - has allowed the use of concrete in abundance only with the beginnnig of the 20 th century. Today reinforced concrete is the primary structural material of all significant engineering and architectural constructions ranging from dams to apartment buildings. I. Concrete: a) Physical Properties: Density of concrete: 2000 kg/m3 (must learn) b) Concrete as a cementitious material In English the term “cementitious” material includes those which mixed with water first to form a paste. Aggregate may or may not be added. The paste is temporarily plastic and maybe moulded or deformed. But later it hardens or sets into a rigid mass. These cementitious materials are: -cements, -limes, -gypsum. The major role of cement is as part and as a binding material of concrete. Concrete consists of: cement, water and aggregates. Aggregates are defined as follows: inert (it does not take part in any chemical process) material, which when bonded together into a conglomerated mass by a matrix, forms concrete. Aggregate include sand, gravel, crushed stone or light weight aggregate, such as perlite, to obtain a better thermal insulation due to the loss of strength. Cement mixed with fibres produces fibre cement sheets: plain, corrugated or moulded. Thus concrete is an intimate mixture of mineral aggregate and the binding material, such as Portland cement. Its popularity over the last hundred years has been due to many factors; not the least being the ease with which it can be moulded. To mould concrete it is simply poured between shuttering or framework and left to set. c) The manufacturing process of concrete products: Concrete can be mixed by hand or by machine. To obtain correct proportion of material, a gauge box is used. Thus for 4:2:1 mix, 4 boxes of coarse aggregate, 2 boxes of fine aggregate and sand, 1 box of cement are measured mixed together. The water-cement ratio in Hungary is0,45, in the tropics is it is usually 0,5-0,55. Dry materials take up approximatively 50 % more space before being mixed with water into concrete and compacted into position. For placing concrete, the framework must be cleaned out and brushed with mould oil or white – washed (both have a bound-breaking effect), in order to facilitate striking. Compacting can be done either by hand or by mechanical means. After the concrete is set itis necessary to keep it moist for several days in order that it can be thoroughly cured. This enables the strength of the concrete to increase with the passage of time. It will also increase its impermeability, reduce shrinkage and harden the surface against abrasion. Striking time varies with the climate, and type of cement, etc. Vertical formwork can be removed after two days, horizontal after three, while beams and slabs need to be propped without shuttering for a further week. II. Reinforced Concrete a) Physical Properties: Density of reinforced concrete: 2400 kg/m3 (must learn) The observation that concrete first has a plastic past consistency, which can take up the shape of any mould and can incorporate anything with considerable adhesion gave the idea that the insufficient tension –strength of the concrete, which is far behind its compressive strength, could be substituted by inserting steel bars into all parts of the concrete elements, wherever tensile stresses emerge. This is termed “reinforced concrete” and abbreviated as LECTURE PRACTICAL week Topics Topics 8. Building materials and their applications: CONCRETE, REINFORCED CONCRETE
Transcript of TOPIC SCHEDULE week
TOPIC SCHEDULE
Today’s Lecture: Building materials: Concrete and Reinforced concrete A form of cement was used even in roman times, however, the development of building materials and engineering techniques - especially our knowledge on reinforced concrete - has allowed the use of concrete in abundance only with the beginnnig of the 20th century. Today reinforced concrete is the primary structural material of all significant engineering and architectural constructions ranging from dams to apartment buildings. I. Concrete: a) Physical Properties: Density of concrete: 2000 kg/m3 (must learn)
b) Concrete as a cementitious material In English the term “cementitious” material includes those which mixed with water first to form a paste. Aggregate may or may not be added. The paste is temporarily plastic and maybe moulded or deformed. But later it hardens or sets into a rigid mass. These cementitious materials are: -cements, -limes, -gypsum. The major role of cement is as part and as a binding material of concrete. Concrete consists of: cement, water and aggregates. Aggregates are defined as follows: inert (it does not take part in any chemical process) material, which when bonded together into a conglomerated mass by a matrix, forms concrete. Aggregate include sand, gravel, crushed stone or light weight aggregate, such as perlite, to obtain a better thermal insulation due to the loss of strength. Cement mixed with fibres produces fibre cement sheets: plain, corrugated or moulded. Thus concrete is an intimate mixture of mineral aggregate and the binding material, such as Portland cement. Its popularity over the last hundred years has been due to many factors; not the least being the ease with which it can be moulded. To mould concrete it is simply poured between shuttering or framework and left to set. c) The manufacturing process of concrete products: Concrete can be mixed by hand or by machine. To obtain correct proportion of material, a gauge box is used. Thus for 4:2:1 mix, 4 boxes of coarse aggregate, 2 boxes of fine aggregate and sand, 1 box of cement are measured mixed together. The water-cement ratio in Hungary is0,45, in the tropics is it is usually 0,5-0,55. Dry materials take up approximatively 50 % more space before being mixed with water into concrete and compacted into position. For placing concrete, the framework must be cleaned out and brushed with mould oil or white – washed (both have a bound-breaking effect), in order to facilitate striking. Compacting can be done either by hand or by mechanical means. After the concrete is set itis necessary to keep it moist for several days in order that it can be thoroughly cured. This enables the strength of the concrete to increase with the passage of time. It will also increase its impermeability, reduce shrinkage and harden the surface against abrasion. Striking time varies with the climate, and type of cement, etc. Vertical formwork can be removed after two days, horizontal after three, while beams and slabs need to be propped without shuttering for a further week. II. Reinforced Concrete a) Physical Properties: Density of reinforced concrete: 2400 kg/m3 (must learn) The observation that concrete first has a plastic past consistency, which can take up the shape of any mould and can incorporate anything with considerable adhesion gave the idea that the insufficient tension –strength of the concrete, which is far behind its compressive strength, could be substituted by inserting steel bars into all parts of the concrete elements, wherever tensile stresses emerge. This is termed “reinforced concrete” and abbreviated as
LECTURE PRACTICAL week Topics Topics
8.
Building materials and their applications: CONCRETE, REINFORCED CONCRETE
R.C. This concept of a composite structure provided unique properties, which example its rapid, and multilateral application. Current development of reinforced concrete products focus on the enchancement of the processes and the end products of the materials (concrete enchancement with resins, reinforcement with glass, carbon fibres, pre tensioning etc.) b) Types of reinforced concrete products (simple, must-learn list): Structural: pre-manufactured stairs, beams, pillars, slab elements and combinations on-site manufactured 3d concrete structures combination: on-site manufacturing of built-in elements Other: pre-manufacturing of decorative elements other manufactured concrete products (concrete blocks, units etc.) LEARN COMPONENTS OF SKELETON FRAME STRUCTURES FROM ENCLOSED EXAMPLES, BE PREPARED TO SKETCH AND NAME COMPONENTS. APPLICATIONS FIELDS OF CONCRETE AND REINFORCED CONC RETE (must-learn simple list) 1. Load bearing and supporting constructions 1.1. Load bearing beams (big height for shorter span and smaller loads) 1.2. Load bearing walls, columns 2. Concrete coverings 2.1. Floor coverings 2.2. Wall coverings
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PRE-FABRICATED STRUCTURES:
